A study by researchers in San Francisco shows that the risk to men of acquiring HIV through unprotected oral sex with another man is extremely low, with a near-zero chance of infection, aidsmap.com reports. The study, published in the November edition of the journal AIDS, surveyed 239 men who reported engaging only in oral sex with other men. On average, the men in the study had had receptive oral sex with three different men during the previous six months. The overwhelming majority--98%--of oral sex was performed without a condom, and 35% of men reported getting semen in their mouths, 70% of whom swallowed. None of the men in the study tested positive for HIV antibodies.

"The absence of HIV infection detected in this sample confirms...that orally acquired HIV infection is rare," wrote the investigators. However, the researchers acknowledge that their study sample was relatively small and "therefore, we cannot rule out the possibility that the probability of infection is indeed greater than zero."

The study contradicts widely reported previous research, also conducted among gay and bisexual men in San Francisco, that suggested that up to 8% of all HIV infections among men who have sex with men were linked with unprotected oral sex.